haskell - 如何压缩不同长度的列表？

Question

如何压缩两个列表，例如

["Line1","Line2","Line3"]
["Line4","Line5"]

不丢弃第一个列表中的其余元素？

如果可以的话，我想用空列表压缩额外的元素。

Answer 1

zipWithPadding :: a -> b -> [a] -> [b] -> [(a,b)]
zipWithPadding a b (x:xs) (y:ys) = (x,y) : zipWithPadding a b xs ys
zipWithPadding a _ []     ys     = zip (repeat a) ys
zipWithPadding _ b xs     []     = zip xs (repeat b)

只要有元素，我们就可以简单地对它们进行压缩。一旦我们用完元素，我们只需使用填充元素的无限列表来压缩剩余列表。

在您的情况下，您可以将其用作

zipWithPadding "" "" ["Line1","Line2","Line3"] ["Line4","Line5"]
-- result: [("Line1","Line4"),("Line2","Line5"),("Line3","")]